Shading/Fill on background when None should be transparent

This is particularly pertinent to V8 now that we are able to float sheets on top of others in dashboards. We should be able to set the background shading to none, equaling transparent, not the shading of the background. It would also be handy when exporting EMFs to PPT etc. and you want the background to disappear (you can ungroup an EMF but this would be easier).